Security camera footage reportedly shows someone entering the museum through a window during the night.

"This is a serious crime to the heritage of humanity," Christophe Girard, deputy culture secretary at the Paris Town Hall, told a news conference.

The theft was committed by "one or more individuals who were obviously organised", Mr Girard said.

He added that investigators were looking into how the museum's security system and several guards were outsmarted by the thief or thieves.

Mr Girard put the value of the stolen paintings at just under 100m euros (£86m; $123m). They had earlier been estimated to be worth some 500m euros (£431m; $618m).

The five missing paintings are Dove with Green Peas by Pablo Picasso (painted in 1911), Pastoral by Henri Matisse (1906), Olive Tree near l'Estaque by Georges Braque (1906), Woman with Fan by Amedeo Modigliani (1919) and Still Life with Candlestick by Fernand Leger (1922).

Broken padlock

Museum officials discovered the theft early on Thursday, when they found a smashed window and a broken padlock which had been cut to gain access to the five paintings.

GREAT ART HEISTS

February 2008: Four paintings by Cezanne, Degas, Van Gogh and Monet are stolen from the EG Buehrle Collection, a private museum in Zurich. The Van Gogh and Monet paintings were recovered

August 2004: Two paintings by Edvard Munch, The Scream and Madonna, are stolen from the Munch Museum in Oslo. Recovered two years later

April 1991: Twenty paintings are stolen from the Van Gogh Museum in Amsterdam. Found shortly afterwards in abandoned car nearby

March 1990: Works by Vermeer, Rembrandt and Manet are stolen from the Isabella Stewart Gardner Museum in Boston. Still lost

It is the biggest heist since the 1990 theft at the Isabella Stewart Gardner Museum in Boston of a Vermeer, several Rembrandts, Degas and other masterpiece.

None of these works has yet been recovered.

Though there is often speculation that works have been "stolen to order" for dishonest collectors, experts in the field say that in reality this is very unusual.

Investigators think that international criminal gangs use art works effectively as a form of currency.

For criminals dealing in drugs or weapons, a rolled-up painting is a way of carrying very large amounts of "currency", even if it is one tenth of the value at auction, the BBC's arts correspondent adds.

The Museum of Modern Art of the City of Paris, located in the east wing of the Palais de Tokyo building, is separate from the bigger and better-known national collection of modern art at the Pompidou Centre.

ANALYSIS: WHAT THE PICTURES TELL US.

If you wanted to start a museum of modern art these five paintings would be high on your list of acquisitions. Between them they tell the story of modern art's emergence, says the BBC arts editor Will Gompertz.

PASTORAL BY HENRI MATISSE (1906)

Image caption
Pastoral painted by Henri Matisse in 1906

Henri Matisse's Pastoral has the hallmarks of the Impressionists - painted outside or "en plein air", with loose brushstrokes and an everyday, realistic subject.

What marks it out from the work of the early Impressionists is the bright, unnatural colours, which he has used to express the scene as he sees and feels it.